Unit 4 Structural Design

1、 Specialized English for Civil Engineering 实用土木工程专业英语实用土木工程专业英语 中国建材工业出版社中国建材工业出版社 Unit 4 Structural Design 第四章 结构设计 Main contents Text APhilosophy of Structure Design结构设 计原理 Translate some important sentences 翻译句子 Special difficulties 难点讲解 Translation Skills -长句的语法分析充分 理解 Writing Skills -标题的语法规则 Te

2、xt APhilosophy of Structure Design Lets see some drawings of structural design. Translate Text A into Chinese. A structure engineering project can be divided into three phases: planning, design, and construction. 结构工程项目可分为三个阶段：规划、设 计和施工。 Structural design involves determining the most suitable propo

3、rtions of a structure and dimensioning the structural elements and details of which it is composed. This is the most highly technical and mathematical phase of a structural engineering project, but it cannot and certainly should not-be conducted without being fully coordinated with the planning and

4、construction phases of the project. 结构设计内容包括确定结构最优的比例尺寸，并确定 结构构件和细部构造的尺寸。这是整个结构工程项目 中技术性最高，数学严谨性最强的阶段，但若不能同 项目的规划和施工阶段充分协调配合，就不能也不应 该进行结构设计。 The successful designer is at all times fully conscious of the various considerations that were involved in the preliminary planning for the structure and, lik

5、ewise, of the various problems that may later be encountered in its construction. 成功的设计师总是会全面考虑结构在初步规 划中所涉及到的各种事项，以及在以后的施 工中会碰到的各种问题。 Specially, the structural design of any structure first involves the establishment of the loading, and other design conditions that must be resisted by the structure

6、and therefore must be considered in its design. Then comes the analysis (or computation) of the internal gross forces (thrust, shears, bending moments, and twisting moments), stress intensities, strains, deflections, and reactions produced by the loads, temperature, shrinkage, creep, or other design

7、 conditions. 在结构设计中应首先确定结构所必须承受因而也必须考虑的荷 载和其它设计状况。然后需要分析(或计算) 总内力(轴力,剪力, 弯矩,和扭矩)，应力强度、应变、挠度和反力等，它们是由荷 载、温度变化、干缩、徐变或其它设计状况所引起的。 Finally comes the proportioning and selection of materials of the members and connections so as to resist adequately the effects produced by the design conditions. The crite

8、ria used to judge whether particular proportions will result in the desired behavior reflect accumulated knowledge (theory, field and model test, and practical experience, intuition, and judgment. 最后确定各构件及连接的尺寸并选择其材料，以抵 抗设计状况所产生的作用效应。当判断某些特定部 位的设计是否符合要求时，就要用到一些经验知识 （理论，现场及模型试验，和实际经验） ，和直观 判别的方法。 For

9、 most common civil engineering structures such as bridges and buildings, the usual practice in the past has been to design on the basis of a comparison of allowable stress intensities with those produced by the service loadings and other design conditions. 对诸如桥梁和建筑物等最常见的土木工程结构而言 ，过去的惯例是设计必须以容许应力强度和由

10、工作 载荷及其他设计状况产生的应力强度之间的对比做 为基础。 This traditional basis for design is called elastic design because the allowable stress intensities are chosen in accordance with the concept that the stress or strain corresponding to the yield point of the material should not be exceeded at the most highly stressed p

11、oints of the structure. 由于在选择容许应力时依据了如下概念即：结构的 最大应力或应变不得超过材料屈服应力或应变，因 此这种传统的设计方法被称为弹性设计。 Of course, the selection of the allowable stresses may also be modified by a consideration of the possibility of failure due to fatigue, buckling, or brittle fracture or by consideration of the permissible defle

12、ctions of the structure. 当然, 考虑到由于疲劳,纵向弯曲，脆性断裂 带来的失效可能性，以及结构容许挠度等因 素，可对容许应力值的选择进行修正。 Depending on the type of structure and the conditions involved, the stress intensities computed in the analytical model of the actual structure for the assumed design conditions may or may not be in close agreement

13、with the stress intensities produced in actual structure by the actual conditions to which it is exposed. 根据结构类型和设计状况不同，采用实际结构的分 析模型，在假想的设计状况下计算出的应力强度和 实际结构在实际状况下产生的应力强度，可能相符 也可能不相符。 The degree of correspondence is not important, provided that the computed stress intensities can be interpreted in te

14、rms of previous experience. The selection of the service conditions and the allowable stress intensities provides a margin of safety against failure. 只要计算出的应力强度能根据以往的经验来解释， 其相符程度就不是很重要。(结构的)使用状况和容 许应力强度的选择为抵抗(结构)失效提供了安全储 备。 The selection of the magnitude of this margin depends on the degree of uncer

15、tainty regarding loading, analysis, design, materials, and construction and on the consequences of failure. For example, if an allowable tensile stress of 20000 psi is selected for structural steel with a yield stress of 33000 psi, the margin of safety (or factor of safety) provided against tensile

16、yielding is 33000/20000. or 1.65. 安全储备大小的选择取决于相关荷载、 分析、 设计 、 材料、 施工和失效后果的不确定性程度。比如： 对于结构钢，屈服应力为 33000磅/平方英寸，而容许 拉应力为 20000磅/平方英寸，那么为受拉屈服提供的 安全储备（安全系数）为 33000/20000，或 1.65。 The allowable-stress approach has an important disadvantage in that it does not provide a uniform overload capacity for all part

17、s and all types of structures. As a result, there is today a rapidly ） growing tendency to base the design on the ultimate strength and serviceability of the structure, with the older allowable-stress approach serving as an alternative basis for design. 容许应力法有一个很大的缺点，就是不能对各种类型 的结构及其各部分，提供相同的超载能力。因此，

18、目 前更趋向于以结构的极限强度和适用性为基础的设计 ，这使得以往以容许应力法为基础的设计只能成为可 选方案 之 一 。 The newer approach currently goes under the name of strength design in reinforced-concrete design literature and plastic design in steel- design literature. 最新的设计方法在钢筋混凝土设计文献中被 称为强度设计，在钢结构设计文献中被称为 塑性设计。 When proportioning is done on the str

19、ength basis, the anticipated service loading is first multiplied by a suitable load factor (greater than 1), the magnitude of which depends upon the uncertainty of the loading, the possibility of its changing during the life of structure, and, for a combination of loadings，the likelihood, frequency,

20、 and duration of the particular combination. 按照强度方法设计构件尺寸时，首先将预期使用荷载 乘以适当的大于1的荷载分项系数，该系数值的大小 取决于荷载的不确定性、其在结构寿命周期中发生变 化的概率。对于某个特定的荷载组合，则取决于该组 合的可能性、频率及持续时间。 In this approach for reinforced-concrete design, the theoretical capacity of a structural element is reduced by a capacity-reduction factor to p

21、rovide for small adverse variations in material strengths, workmanship, and dimensions. 当这种方法应用于钢筋混凝土设计时，鉴于材 料强度，制作工艺，截面尺寸等不利的误差， 结构构件的理论承载能力应乘以承载能力折减 系数。 The structure is then proportioned so that, depending on the governing conditions, the increased load would(1) cause a fatigue or a buckling or a

22、 brittle fracture failure or (2) just produce yielding at one internal section (or simultaneous yielding at several section) or (3) cause elastic-plastic displacement of the structure or (4) cause the entire structure to be on the point of collapse. 随后，考虑到增大后的荷载可能会引起疲劳、压曲 或脆断破坏在某截面发生屈服（或在几个截面上同 步屈服）

23、引起结构的弹塑性位移引起整个结构倾 覆因此，根据以上这些控制条件确定结构尺寸。 Proponents of this latter approach argue that it result in a more realistic design with a more accurately provided margin of strength over the anticipated service conditions. These improvements result from the fact that non-elastic and nonlinear effects that b

24、ecome significant in the vicinity of ultimate behavior of the structure can be accounted for. 后一种方法（塑性设计）的倡导者提出，这种方法能 够在预期的使用状况下提供更明确的强度储备，是一 种更实用的设计方法。这种改善取决于考虑了非弹性 和非线性效应，这两种效应在结构接近临界状况时变 得非常显著。 In recent decades, there has been a growing concern among many prominent engineers that not only is the

25、 term “factor of safety” improper and unrealistic, but worse still a structural design philosophy based on this concept leads in most cases to an unduly conservative and therefore uneconomical design, and in some cases to an unconservative design with too high a probability of failure. 最近几十年，在许多著名的工

26、程师当中，有一个顾虑 已经越来越明确。那就是不但“安全系数”这个名词 已不再恰当，也不符合实际，而且更糟糕的是，以此 概念为基础的结构设计方法，在许多情况下会导致一 个过度保守、不经济的设计，而在某些情况下产生一 个不保守且失效概率很高的设计。 They argue that there is no such thing as certainty, either of failure or of safety of a structure but only a probability of failure or a probability of safety. They feel, there

27、fore, that the variations of the load effects and the variations of structural resistance should be studied in a statistical manner and the probability of survival or the probability of serviceability of a structure estimated. 他们认为结构的失效和安全都不是确定， 只存在失效 概率和可靠概率。因此,他们觉得应该用统计学的方法 来研究荷载效应变量和结构抗力变量并估计结构安全

28、 性与适用性的概率。 It may not yet be practical to apply this approach to the design of each individual structure. However, it is believed to be practical to do so in framing design rules and regulations. It is highly desirable that building codes and specifications plainly state the factors and correspondin

29、g probabilities that they imply. 对每一个具体结构都采用这种设计方法还不是 很现实，但在制定设计规范时还是很实用的。 对于建筑条例和技术规程来说，明确规定相关 系数及其蕴涵的相应概率，这是非常必要的。 Translate the following sentences from English into Chinese. （1） Structural design involves determining the most suitable proportions of a structure and dimensioning the structural el

30、ements and details of which it is composed. （2） The successful designer is at all times fully conscious of the various considerations that were involved in the preliminary planning for the structure and, likewise, of the various problems that may later be encountered in its construction. （3） Dependi

31、ng on the type of structure and the conditions involved, the stress intensities computed in the analytical model of the actual structure for the assumed design conditions may or may not be in close agreement with the stress intensities produced in actual structure by the actual conditions to which i

32、t is exposed. （4） The selection of the service conditions and the allowable stress intensities provides a margin of safety against failure. （5）The allowable-stress approach has an important disadvantage in that it does not provide a uniform overload capacity for all parts and all types of structure.

33、 Keys： (1)结构设计包括确定结构最合适的比例，以及标出构 件的尺寸和构件的组成细节。 (2)好的设计师总能充分考虑到建筑结构前期设计的各 种因素，以及施工过程中可能遇到的各种问题。 (3)根据结构的类型和相关条件，从为预期设计条件而 进行的实际结构的分析模型所计算出来的应力强度与 实际结构在实际条件中产生的应力强度有可能基本一 致或不一致。 (4)操作条件和容许应力强度的选择能提供了一个对抗 失效的安全系数。 (5)容许应力法有一个明显的劣势，即它无法为各类结 构及结构的所有部分提供一个统一的过载。 Special difficulties 难点讲解难点讲解 1 For most co

34、mmon civil engineering structures such as bridges and buildings, the usual practice in the past has been to design on the basis of a comparison of allowable stress intensities with those produced by the service loadings and other design conditions. 译文：对诸如桥梁和建筑物等最常见的土木工程结构而言， 过去的惯例是设计必须以容许应力强度和由工作载荷及

35、其他 设计条件产生的应力强度之间的对比为基础。 available意思是“可用的”“有空的”“可会见的”，有时 放在名词后面作后置定语。例如： No funding will be available until the technology is completely proven. 该技术得到充分验证后才会有拨款。 2 Of course, the selection of the allowable stresses may also be modified by a consideration brittle of the possibility of failure due to f

36、atigue, buckling, or fracture or by consideration of the permissible deflections of the structure. 译文：当然，容许应力的选择可能会因由疲劳、弯曲或脆性 断裂造成的应力失效得到调整，也有可能因考虑到结构允许 挠度而被调整。 （1）modify意思是“修改”“修饰”。例如： We have to modify our plan a little bit. 我们得对我们的计划稍加修改。 （2）due to相当于“because of”，意思是“由于”“因为 ”“应给予”“应归于”。例如： His mi

37、stake was due to youth and inexperience. 他失误的原因是年轻没有经验。 3 Proponents of this latter approach argue that it results in a more realistic design with a more accurately provided margin of strength over the anticipated service conditions. 译文：后一种方法的倡导者认为它将带来更符合现实的 设计，为以后的服役条件更精准地提供强度系数。 （1）argue意思是“坚决主张”“

38、提出理由证明”“表 明”“证明”。例如： Intel would argue that its performance. 英特尔会争辩 说他们改善了性能。 （2）result in意思是“引起”“导致”“致使”。 They result in poor capital allocation. 它们会导致资本 配置不当。 Translation Skills 长句的语法分析充分理解 科技英语的特点之一是句子较长且结构复杂。长句 多呈树形结构，以主谓形式构成句子的主干，其他 成分则附于主干之上，各层次之间错落有致。因此 ，长句较难翻译，翻译时要理清句子内部各层次之 间的逻辑关系，还要求对原文理解透

39、彻。在翻译长 句时，语法分析是至关重要的一步。首先应该对句 子进行细致的语法分析，辨别句子的主干结构和层 次关系，然后再运用各类翻译技巧将其转化为符合 汉语习惯的译文。 【例1】The properties of concrete depend substantially on the proportions of the mix, on the thoroughness with which the various constituents are intermixed, and on the conditions of humidity and temperature in which t

40、he mix is maintained from the moment it is placed in the forms until it is fully hardened. 句子主干：The properties depend on the p r o p o r t i o n s o f t h e m i x , o n t h e thoroughness, and on the conditions of humidity and temperature. 句子层次关系：The properties of concrete depend substantially on the proportions of the mix, on the thoroughness【with which the various constituents are intermixed】（定语从句，修饰